Immune System Introduction PDF

IMMUNE SYSTEM Anna Rees OUTLINE INTRODUCTION TO THE IMMUNE Loading… SYSTEM INTENDED LEARNING OUTCOMES DEFENCE PROVIDED BY SKIN AND EPITHELIUM OF AIRWAYS AND GUT Provide physical defence against infection by bacteria, viruses, fungi and parasites Skin contains sweat glands a...

IMMUNE SYSTEM Anna Rees OUTLINE INTRODUCTION TO THE IMMUNE Loading… SYSTEM INTENDED LEARNING OUTCOMES DEFENCE PROVIDED BY SKIN AND EPITHELIUM OF AIRWAYS AND GUT Provide physical defence against infection by bacteria, viruses, fungi and parasites Skin contains sweat glands and Loading… sebaceous glands that secrete fatty acids that inhibit the growth of bacteria on the skin surface MUCOCILIARY ESCALATOR Physical defence against pathogens entering the lungs FUNCTION OF THE IMMUNE SYSTEM AUTOIMMUNE DISEASES E.g. rheumatoid arthritis ORGAN TRANSPLANTS E.g. heart transplant Risk of organ rejection Immunosuppressive medication needed  Innate immune system - present from birth - inflammatory response IMMUNE - fast - non-specific SYSTEM – Acquired/adaptive immunity 2 PARTS - specific - slower - powerful (has memory) - builds over time  Physical defence Why the immune system is needed Simple function of the immune system SUMMARY Loading… Immune system is in two parts Next..innate system INNATE IMMUNE RESPONSE  INTENDED LEARNING OUTCOMES Describe of each of the following chemicals which are involved in innate immunity and include their function Surface chemicals, Histamine, Kinins, Interferon, Complement, Prostaglandins, Leukotrienes, Pyrogens Describe the inflammatory response, when this response is initiated, how it is initiated, and its purpose. Describe the four cardinal signs of inflammation, the mechanism which leads to these signs, and the role that this mechanism plays in the immune response? Describe the role of fever and the mechanism by which this is brought about. Name the cells involved in non-specific phagocytosis in the innate immune response and describe this. Describe natural killer cells, their mode of action and the role they play in the innate immune response? Briefly outline the complement mechanism and the role this plays in the immune response. INFLAMMATION 4 cardinal signs Heat Redness Swelling Pain FEVER Elevated temperature, caused by pyrogen which acts on the hypothalamus Hypothalamus Thermoregulatory centre Has set temperature (36.9 degrees Celsius) Resets set point Mediated by prostaglandin-E2 Antipyretics e.g. paracetamol reduce amount of PGE2 made, therefore reduce fever FEVER – BENEFITS AND COST Benefits – leucocytes work better with increased temperature, some bacteria work worse Cost – Can cause brain damage and causes a person to feel unwell NON-SPECIFIC PHAGOCYTOSIS Macrophages, neutrophils, dendritic cells Eliminates entire cells by phagocytosis  NON-SPECIFIC PHAGOCYTOSIS CONTINUED… Pattern recognition receptors (PRRs) embedded in the phagocyte match molecules called PAMPs (pathogen associated molecular markers). These PAMPs are found on pathogens. Relatively few PRRs are needed as PAMPs are common across a wide range of pathogens The PRR on the e.g. macrophage binds with the PAMP. This initiates phagocytosis, and also causes the release of cytokines and cytotoxins The phagocyte (e.g. macrophage) breaks up the pathogen and then displays an antigen on its MHC (major histocompatibility complex). In this way the antigen (from the pathogen which has been phagocytosed) is being shown to other cells. There are two types of MHC (1 and 2). All `nucleated cells have MHC-1s which are specific for that person. Red blood cells (RBCs) do not have MHC-1. MHC1 and 2 are important in the acquired immune response.  NATURAL KILLER CELLS Natural killer cells are a type of lymphocyte ( 2% of lymphocyte population) They are non-specific Identify self-cells that lack MHC-1 (don’t attack RBCs) or target injured, infected or cancer cells that are expressing PAMP like molecules All our cells should have MHC-1, but some viruses or cancers cause our cells to not have MHC- 1 Natural killer cells produce perforins (chemicals which create pores in the cell being targeted) and granzymes (which enter the cells through channels created by the perforins and then destroy the cell). This programmed cell death is called apoptosis The cells are killed, macrophages are then activated that remove the debris  COMPLEMENT Complement is a group of 20 proteins that normally circulate the blood in an inactive, non- functional form. They become activated in the complement cascade, a series of reactions in which each component of the series activates the next component Activated complement proteins provide protection in several ways Some attach to a form a hole in the membrane of bacterial cells, resulting in lysis of the cell Complement proteins attached to the surface of bacterial cells can also stimulate macrophages to phagocytize the bacteria Complement proteins attract immune system cells to sites of infection and promote inflammation SUMMARY 5 strategies used by innate immune system to respond to infection Inflammation Fever non-specific phagocytosis natural killer cells complement CHEMICALS Chemical Description (include function) INVOLVED Surface chemicals Lysozymes (in tears, saliva, nasal secretions and sweat) lyse cells; acid secretions (sebum in the skin and hydrochloric acid in the stomach) prevent microbial growth or kill microorganisms; mucus on the mucous membranes traps microorganisms so IN INNATE that they cannot be released IMMUNITY Histamine An amine released from mast cells, basophils and platelets; histamine causes vasodilation, increases vascular permeability, stimulates gland secretions (especially mucus and tear production), causes smooth muscle contraction of airway passages (bronchioles) in the lungs, and attracts eosinophils. Kinins Polypeptides derived from plasma proteins; kinins cause vasodilation, increase vascular permeability, stimulate pain receptors and attract neutrophils Interferon A protein produced by most cells that interferes with virus production and infection Complement A group of plasma proteins that increase vascular permeability, stimulate the release of histamine, activate kinins, lyse cells, promote phagocytosis and attract neutrophils, monocytes, macrophages and eosinophils Prostaglandins A group of lipids, produced by mast cells that causes smooth muscle relaxation and vasodilation, increases vascular permeability and stimulates pain receptors Leukotrienes A group of lipids, produced primarily by mast cells and basophils, that causes prolonged smooth muscle contraction (especially in the lung bronchioles), increases vascular permeability and attracts neutrophils and eosinophils Pyrogens Chemicals, release by neutrophils, monocytes and other cells that stimulate fever production  ACQUIRED (ADAPTIVE) Anna Rees IMMUNITY INTENDED LEARNING OUTCOMES Briefly outline the acquired immune response Describe the Humoral (antibody-mediated) response Describe the Cell-mediated response  Innate response is generalised ACQUIRED Acquired response is slow but powerful and has VS INNATE memory Two categories of adaptive immunity RESPONSE Humoral (antibody-mediated) Cell-mediated  Humoral Cell mediated Mediated by B lymphocytes T lymphocytes Originates in Loading… Bone Marrow Bone Marrow Matures in Bone Marrow Thymus receptor Antibody T-Cell receptors HUMORAL RESPONSE CELL MEDIATED RESPONSE SUMMARY Acquired immune response made up of the humoral and cell-mediated responses